Power plant



Dec. 28, 1937. M. H. KUHNER 2,103,685

POWER PLANT Filed NOV. '7, 1955 HIGH Pnsssuns TURBINE Low PRESSURE -TURBINE grw cmi w MAX .H. KUHNER Patented Dec. 28, 1937 ATENT POWER PLANT Max H. Kuhner, Worcester, Mass, assignor to 1 Riley Stoker Corporation, Worcester, Mass, a ccrporaticn of Massachusetts Application November 7, 1935, Serial No. 48,723

' "7 Claims.

This invention relates topower plants, and more particularly to power plants of the type having a plurality of steam motors through which steam is passed successively.

Steam power plants as designed and constructed a few years ago were ordinarily arranged to generate and utilize steam at comparatively mod-' erate pressures and temperatures. Many such plants are in use at the present time and in good operating condition. It sometimes becomes necessary to increase the capacity of one of these low pressure plants because of increasing'loads, and one way to accomplish this is by installing a new high pressure boiler and turbine, the turbine being arranged to exhaust into the existing low presing that for which the turbine was designed, and

for this reason comparatively few plants have taken advantage of this means for increasing j their capacity and efficiency.

It is accordingly one object of the invention to provide a steam powerplant having a high pressure steam motor exhaustinginto a low pressure steam motor, and to so arrange the various parts that the low pressure motor will be protected from high steam temperatures under varying load conditions.

It is a further object of the invention to provide an improved method of generating power from steam whereby high capacity and efficiency may be obtained and the temperature of the steam at variousstages may be controlled accurately.-

. With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts and the steps of the process set forth in the specification and covered by the claims appended hereto.

Referring to the drawing illustrating one embodiment of the invention, and in which like reference numerals indicate like parts, the single figure is a somewhat diagrammatic elevation of a steam power plant.

The embodiment illustrated comprises a high pressure steam boiler it of the water tube type having a front water drum H and a superheater l2. The superheater delivers steam at a high temperature to a headerv l4 which is connected by a pipe l5 to a high pressure motor or turbine It. The turbine 16 exhausts through a pipe I8 into a low pressure motor or turbine [9. A low pressure boiler 20 is shown connected by a pipe 22 to the pipe E8, the pipe 22 having a valve 23 therein which can be closed when the boiler 26 is not in use. The boiler IE] serves to generate steam at a high pressure and a high temperature, and this steam is expanded successively through the turbines it and I9, producing power much more efiiciently than would be possible with the low pressure turbine i9 alone. It will be understood that the low pressure turbine l9 and boiler 29 may have been installed several years before the remained of the apparatus, which may have been added to increase the capacity and efficiency of the original installation. The boiler 20 is not necessary to the operation of the revamped power plant, and hence this boiler can be'removed or it can be retained as a stand-by.

With the power plant as so far described there will be a tendency for the temperature of the exhaust steam fromthe high pressure turbine it to increase considerably as the load decreases. This creates a dangerous situation, since the low pressure turbine I9 is not adapted to withstand high steam temperatures.

In order to overcome this difficulty, I preferably provide means to maintain the steam entering the low pressure turbine at a substantially constant temperature under varying load conditions, and I preferably control this temperature by varying the temperature of the steam entering the high pressure turbine. This variation in temperature is effected by a suitable desuperheater. In the drawing there is shown a desuper-- heater mounted in the boiler drum ii and in contact with the water therein. A slight restriction 2% isprovided in the superheated steam .pipe it (by means of an orifice plate or otherwise) to cause a slight drop in the steam pressure at this point. The desuperheater inlet pipe 2'! is connected to the pipe I5 anterior to the restriction 26,

and the desuperheater outlet pipe 29 is connectedto the pipe I5 posterior to therestriction. It will be noted that the portion of thleapipe i5 located between the pipes 21 and 29 forms a by-pass for the desuperheater. The relative rates of flow in the desuperheater and its by-pass are controlled by means of a valve 30 located in one of the pipes connected with the desuperheater (in the present instance the outlet pipe 29). This valve SEQ is controlled in accordance with variations in the temperature'of the steam entering the low pressure turbine [9, to minimize-such variations. For

this purpose I mount a temperature'responsive bulb 32 in the pipe 18, preferably posterior to the point at which the pipe 22 is connected thereto, and I connect this bulb by means of a small tube 33 to a suitable relay 34 of any well known construction, The relay 34 is supplied with air or other fluid under pressure through a pipe 35, and the relay is connected to the valve 30 by means of a pipe 36. These various parts are so constructed and arranged that if the steam temperature at the bulb S2 exceeds a predetermined value an impulse will be transmitted through the tube, 33 to the relay 34, which will thereupon change the control pressure in the pipe 36 and. cause the valve 30 to open, allowing a larger proportion of the steam to pass through the desuperheater 25. This will reduce the temperature of the steam entering the high pressure turbine '16, and the desired temperature will be restored at the entrance of the low pressure turbine l9. It will be noted that this control will be eifective whether the low. pressure boiler 29 is in use or not, and irrespective of variations in the temperature of the steam delivered thereby, so long as the high pressure boiler and turbine are in operation.

The superheater i2 is preferably designed to deliver steam at a fairly constant temperature suitable for direct admission to the high pressure turbine 16. However there is certain to be some variation in the steam temperature with changes in load, methods of firing, etc., and it is therefore desirable to protect the turbine Hi from the possibility of damage from unusually high steam temperatures. For this purpose I have shown a valve 38 which controls a by-pass conduit 39 around the valve 36. A temperature responsive bulb 40 is mounted in the pipe l5 posterior to the point at which the pipe 28' connects therewith,'and a tube 46 connects the bulb 46 with a relay 43 which is supplied with pressure fluid through a pipe 44. The relay 43 is connected to the valve 38 by means of a pipe These various parts are so constructed and arranged that if the steam temperature at the bulb it; exceeds a predetermined value, the relay 43 will open the valve 38 and cool the steam by passing a portion thereof through the desuperheater 25. This will occur even though valve 30 may be fully closed. I

The operation of the invention will now be apparent from the above disclosure. The boiler ill generates steam at a'high pressure and this steam in passing through the superheater I2 is raised to a high temperature. The steam is expanded successively in the turbines I3 and i9, and power is produced efficiently. So long as the steam temperatures at the bulbs 48 and 32 do not exceed the values considered safe for the turbines I6 and I9 respectively, the valves 39 and 39 will remain closed and no steam will pass through the desuperheater 25. If however, due to load changes or for any other reason, the steam temperature at either of these bulbs becomes excessive, the corresponding valve will be opened to allow a portion of the steam to travel through the desuperheater, thus restoring the desired temperature. The restriction 26 produces a sufiicient pressure drop to ensure the necessary rate of flow through the desuperheater when either of the valves is open. The low pressure boiler 20 can be used or not, as may be desired, and the control system will function properly in either case.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The method of producing power from steam comprising the steps of expanding the steam through two stages successively, and controlling the temperature of the steam entering the first stage in accordance with variations inthe temperature of the steam between the stages, to minimize such variations.

2. The method of producing power from steam comprising the steps of expanding the steam through two stages successively, and controlling the temperature of the steam entering the first stage in inverse relationship with the temperature of the steam entering the second stage.

3. The method of producing power from superheated steam comprising the steps of partially desuperheating the steam, subsequently expandingthe steam through two stages successively, and varying the amount of desuperheating in accordance with variations in the temperature of the steam between stages, to minimize such variations.

4. A steam power plant comprising a steam boiler, a high pressure motor receiving steam from the boiler, a low pressure motor receiving steam from the high pressure motor, and means to vary the temperature of the steam entering the high pressure motor in accordance with variations in the temperature of the steam entering the low pressure motor.

5. A steam power plant comprising a steam boiler, a superheater, a desuperheater, a'high pressure motor, a low pressure motor, all of said parts being connected for the passage of steam through them successively in the order named, and means to control'the operation of the desuperheater in accordance with variations in the temperature of the steam entering the low pressure motor.

6. A steam power plant comprising a steam boiler, a superheater, a desuperheater, a high pressure motor, a low pressure motor, all of said parts being connected for the passage of steam through them successively in the order named, a by-pass pipe for the desuperheater, and means to control the relative rates of flow in the desuperheater and by-pass in accordance with variations in the temperature of the steam entering the low pressure motor.

7. A steam power plant comprising a steam boiler, a superheater, a desuperheater, a high pressure motor, a low pressure motor, all of said parts being connected for the passage of steam through them in the order named, and means to control the operation of the desuperheater and increase the amount of desuperheating whenever the temperature of the steam entering either of said motors exceeds a temperature which is predetermined for each motor.

MAX H. KUHNER. 

